LNG production plants are large complex and expensive plants to construct and maintain. Traditional stick-built onshore LNG plants have almost become uneconomic due to the costs involved with acquisition of suitable land, dredging, jetty construction, and labour. Processes involved in the production of LNG such as gas pre-treatment, liquefaction and storage are typically undertaken at a fixed onshore LNG production plant associated with a jetty that is built in sufficiently deep water to allow berthing of the LNG Carriers. it is common practice for the onshore LNG production plant to be entirely constructed on site using a method of construction referred to in the art as “stick-built”. Efforts to reduce this cost have largely been focused on seeking to leverage the economics of scale via increased LNG train capacity size and improvements in LNG Carrier berth utilization.
To avoid the environmental impacts associated with the coastal modifications that often forms part of traditional onshore LNG plants, it has been proposed to produce LNG at sea at an offshore location. In one example of this, the entire LNG production is proposed to be performed on a floating LNG production (“FLNG”) vessel. Given their size and complexity, the costs associated with the implementation of a complete LNG liquefaction plant onboard a FLNG vessel at sea are extremely high. The limited space onboard a FLNG vessel requires that the LNG production facility must be designed to fit within the compact footprint of a barge or vessel and is restricted to a particular fixed feed processing rate, as all available deck space is utilised and optimised to keep the overall size of the floating LNG production vessel to a minimum.
This results in an increased risk being carried compared to onshore plants. The layout issues are further complicated by some of the equipment being sensitive to motion during different sea states, logistics difficulties associated with maintenance, and restricted LNG carrier mooring conditions. There are also large loads placed on plant equipment on such barges as a consequence of wave motion or the impact of waves upon these floating structures which can cause shutdowns during severe weather conditions. Such floating structures can avoid severe weather conditions by shutting down, being disconnected and sailing away which leads to disruption in production and lengthy start up times.
There remains a need for an alternative LNG processing plant that may address one or more of the above-described disadvantages of conventional LNG processing plants.
The above reference to the background art does not constitute an admission that the art forms a part of the common general knowledge of the person of ordinary skill in the art. The above references are also not intended to limit the application of the method and plant as disclosed herein.